CC and CH bond activation of 1,2-propanedioxy by atomic oxygen on Ag(110): Effects of CO-adsorbed oxygen on reaction mechanism

Ayre, Caroline R.; Madix, Robert J.

doi:10.1016/0039-6028(94)90777-3

Cited by 21 publications

(46 citation statements)

References 17 publications

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“…On the basis of these k 12 values, we have calculated the expected ν op (CCO) frequencies of the corresponding 13 C-substituted ketenylidene species together with the as yet unobserved in-phase CdCdO stretching ν ip (CCO) frequencies of all the ketenylidene isotopomers. These results are presented in Table 4, which shows that even with this simple model it is possible to reproduce faithfully the experimentally observed frequency shifts of ν op (CCO) induced by selective 13 The electronic structure of the ketenylidene species on Ag-{111} is a weighted average of the three major canonical forms represented in Figure 8. The primary force constants k 1 and k 2 are smaller and larger than those of alkenes and ketones, respectively, suggesting the dominance of resonance form II (with CsC and CtO bonds) in the ground state.…”

Section: {111}mentioning

confidence: 68%

“…Ag{111} a (cm -1 ) (CH3)2 13 cm -1 ) that are characteristic of acetone enolate lie below our accessible spectral range, as they would have greatly aided in the identification of this surface species. 9 3.2.…”

Section: Adsorption Of Acetone On Preoxidized Ag{111} At 180 Kmentioning

confidence: 97%

“…The calculated frequency ratio for ν(CO): ν(13 CO):ν(C 18 O):ν( 13 C 18 O) is 1:0.978:0.976:0.953 (using a simple valence force field analysis), while that for ν op (CCO): ν op ( 13 CCO):ν op (CC 18 O):ν op ( 13 CC 18 O):ν op (C 13 CO):ν op ( 13 C 13 CO): ν op (C 13 C 18 O):ν op ( 13 C 13 C 18 O) is 1:0.999:0.984:0.982:0.974:0.973: 0.957:0.955. These trends are verified by the findings of the present work, as well as experimental observations of CO stretching frequencies on other metal surfaces.…”

mentioning

confidence: 99%

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Mechanism of Acetone Oxidation on Ag{111}-p(4 × 4)−O

and

King

1996

J. Phys. Chem.

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The decomposition of acetone over preoxidized Ag{111} has been studied using reflection absorption infrared spectroscopy. Propane-2,2-diyldioxy and acetone enolate are formed through O-induced nucleophilic addition and H abstraction at 180 K. Further oxidation occurs rapidly above 220 K via acetone enolate to yield metallacyclic intermediates that break down into ketene and methylenedioxy, which deprotonate to produce stable ketenylidene and formate, respectively. The measured vibrational frequencies of several surface-bound ketenylidene isotopomers have been successfully fit to a modified valence force field analysis. Although ketenylidene and CO adsorbed on a metal surface both exhibit strong absorption features due to ν op (CCO) and ν(CO), respectively, at ∼2000 cm -1 in their vibrational spectra, it is shown that they may still be readily distinguished by selective 13 C or 18 O substitution of their carbonyl atoms only, since this results in pairs of absorption bands that possess frequencies of the opposite order (ν op (C 13 CO) < ν op (CC 18 O) and ν(C 18 O) < ν( 13 CO)). A reaction mechanism has been proposed that accounts for the fact that ketenylidene retains the acetone carbonyl group while formate is wholly derived from the acetone methyl group.

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Section: {111}mentioning

confidence: 68%

Section: Adsorption Of Acetone On Preoxidized Ag{111} At 180 Kmentioning

confidence: 97%

mentioning

confidence: 99%

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Mechanism of Acetone Oxidation on Ag{111}-p(4 × 4)−O

and

King

1996

J. Phys. Chem.

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“…It is proposed that in the presence of metals and under oxygen rich conditions, PG adsorbed onto the metal surface produces 1,2 propylenedioxy at T < 80°C. With higher temperatures, propylenedioxy desorbs from the surface to form MGA via a double dehydrogenation reaction [33–35]. The same intermediate can decompose into FA and AA via C C bond cleavage, through the formation of adsorbed acetate and formate, respectively [22, 36].…”

Section: Discussionmentioning

confidence: 99%

Surface chemistry of electronic cigarette electrical heating coils: Effects of metal type on propylene glycol thermal decomposition

Saliba

Hellani

Honein

et al. 2018

Journal of Analytical and Applied Pyrolysis

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Introduction: Carbonyls, a class of compounds strongly linked to pulmonary disease in smokers, are probably the most reported non-nicotine toxicants found aerosols. Reported emissions vary from negligible quantities to those far exceeding combustible cigarettes. Observations of high emissions are commonly attributed to “dry puffing”, whereby the ECIG heating filament runs dry of liquid and reaches temperatures that induce thermal degradation of the ECIG vapor components at the filament’s metal surface. Using a pyrolysis flow reactor, in this study we examined the potential role of surface chemistry in the formation of carbonyl compounds in ECIGs, and whether the different commercially available filament materials could potentially impact their toxicant emissions through catalysis. This information could inform nascent efforts to regulate the design of ECIGs for public health ends. Methods: Nitrogen or air saturated with propylene glycol vapor was drawn through a temperature and residence time controlled tubular quartz pyrolysis flow reactor in which nichrome, Kanthal, or stainless steel ECIG heating filament wires were inserted. A control condition with no inserted wire was also included. Concentrations of carbonyl products at the reactor outlet were measured as a function of temperature, heating filament wire material, and carrier gas composition (N2 vs air). Carbonyls were sampled using DNPH cartridges and analyzed by HPLC. Results: ECIG heating filament wires were found to have a strong catalytic effect. Carbonyl formation initiated at temperatures lower than 250°C in the presence of the metallic wires, compared to 460°C without them. Carbonyl formation was found to be a function of the material of construction, and whether the wire was new or aged. New nichrome wires were the least reactive, but when aged they exhibited the highest reactivity. Carbonyls were formed via dehydration or oxidation reactions of PG. Conclusions: Carbonyl formation chemistry is catalyzed by commonly used ECIG heating filament materials, at temperatures that are well below those expected during “dry puffing”. The variability in the distribution and yield of carbonyl compounds across ECIG filament materials suggests that this heretofore unaccounted variable may partially explain the wide ranges reported in the literature to date. More importantly, it suggests that ECIG construction materials may be an important variable for regulations designed to protect public health.

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“…This adsorption process has been observed for several other alcohols at, or below the reaction temperature used in the ECCL process. [21][22][23][24][25] Nonetheless, information on the adsorption of diols or higher polyols is very scarce.…”

Section: Figurementioning

confidence: 99%

Liquid-Phase H-Transfer from 2-Propanol to Phenol on Raney Ni: Surface Processes and Inhibition

et al. 2017

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is perhaps the most widely used catalyst for the transformation of biogenic molecules in industrial practice (e.g., as in the production of sugar alcohols and hardening vegetable oils). Currently, Raney Ni has found another key application; the catalytic upstream biorefining (CUB) of lignocellulose in which the soluble products released from the lignocellulosic matrix undergo reductive processes, rendering depolymerized lignin oils in addition to high-quality holocellulosic pulps. Despite the industrial importance of Raney Ni, its surface chemistry is poorly understood. In this study, using the H-transfer reaction between 2-propanol (2-PrOH) and phenol as a model reaction, we studied the influence of various alcohols on the catalytic performance of Raney Ni. For the H-transfer hydrogenation of phenol to cyclohexanol, the inhibition of the catalyst increases in the order of secondary alcohols << primary alcohols < polyols at 130 °C. To better understand the observed inhibition, we also studied the molecular interactions of the various alcohols at the catalytic solid-liquid interface using in situ attenuated total reflection infrared (ATR-IR) spectroscopy. The in situ spectroscopic data revealed that 2-PrOH adsorbs on at least two chemically different sites on the surface of Raney Ni. One of these two adsorption sites was attributed to the Ni site responsible for the saturation of the phenolic ring. The ATR-IR spectroscopic data also shows that the adsorption of phenol involves its hydroxyl group. Notably, the phenolic ring was found to be tilted with respect to the surface. Competitive adsorption of various other alcohols was also investigated at the catalytic solid-liquid interface. The presence of methanol inhibited the adsorption of 2-PrOH to a significantly greater degree than phenol. Therefore, it is proposed that hydrogen transfer hydrogenation of the phenolic ring be inhibited in the presence of additional alcohols mainly due to the competitive adsorption with 2-PrOH. Several polyols were found to interact through a bidentate interaction with the catalyst surface explaining their stronger inhibition, compared to primary alcohols. In a broader context, this study proposes the effect of hemicellulose sugars and sugar alcohols, formed in the CUB process, upon the product selectivity of CUB catalyzed by Raney Ni and using 2-PrOH as an Hdonor.

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CC and CH bond activation of 1,2-propanedioxy by atomic oxygen on Ag(110): Effects of CO-adsorbed oxygen on reaction mechanism

Cited by 21 publications

References 17 publications

Mechanism of Acetone Oxidation on Ag{111}-p(4 × 4)−O

Mechanism of Acetone Oxidation on Ag{111}-p(4 × 4)−O

Surface chemistry of electronic cigarette electrical heating coils: Effects of metal type on propylene glycol thermal decomposition

Liquid-Phase H-Transfer from 2-Propanol to Phenol on Raney Ni: Surface Processes and Inhibition

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